That's exactly what I was waiting for. Tell me something, wasn't Allah capable of decreeing the % of Zakkat to be paid, or the number of rakkat of Namaz to be offered, all in Quran itself?
I can explain the above a hundred different ways, however, best one would be for you to understand, Allah SWT is all understanding and knowing. Quran-e-Kareen is supposed to be for all times, not just for today or yesterday. Try to understand and appreciate the flexibility Allah has gifted you (by building it right into Quran - the vagueness about certain issues - as they are flexible), instead of being so stringent with yourself. Ittidal in everything is the way to go my friend.
Can continue if you wish.